Modern browsers will allow popups when they're launched from an event loop triggered by an explicit user action. Thus, it's perfectly OK (ignoring web design best practices) to open up something like a "Help" section for your website in a separate window if that happens when the user clicks a "Help Me!" button. Also, it's become quite common for sites to use in-page "pseudo windows" to jam content in front of hapless visitors, and browsers really can't do anything to stop that.